How do you use an image in a blender animation?
Import Images as Planes Add-on

This is an add-on bundled with Blender. Go to File > User Preferences > Addons and type Import Images as Planes. Check the add-on to enable it.



Cycles Render

Key Shift + A and select Mesh > Images as Planes. Find the image in the File Browser. On the lefthand side, choose either Diffuse or Emission considering that Emission does not require a light source but does not receive shadows (without a crazy amount of Compositing; see my answer here) and Diffuse does require a light source and, likewise, receives shadows. Click Import Images as Planes.



Blender Render

Key Shift + A and select Mesh > Images as Planes. Find the image in the File Browser. On the lefthand side, either check Shadeless or don't considering that Shadeless does not require a light source but does not receive shadows and not checking Shadeless does require a light source and, likewise, receives shadows. Click Import Images as Planes.